For example, I have a numbered list, what is easier for an average user to read ?

Vertically

[1] [5]
[2] [6]
[3] [7]
[4] [8]

OR

Horizontally

[1] [2]
[3] [4]
[5] [6]
[7] [8]

...assuming columns and rows count matters, how do I make the choice between the two ways of displaying ordered lists. I.e. how long does a row have to be to use one or how long does a column have to be to use the other, is there maybe an ideal ratio to use as a rule of thumb?

what if you have 1000 columns but 2 rows... i'm looking for some sort of formula that allows you to decide between the two
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Sammy GuergachiFeb 25 '13 at 19:08

please clarify if you have no requirement to avoid horizontal scrolling, which is disaster in mobile world. if you have such requirement so you are limited with your application window width. even in such case it's hard to calculate column number because you need to do it using real text width. in other words you are dependant of window width but not of abstract ratio between columns and rows.
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SergFeb 25 '13 at 19:52

I would not scroll horizontally at all. I would list them vertically not matter how many items are in the list
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Charles WesleyFeb 25 '13 at 20:21

I think it still depends on some factors. If the list just groups some records, just to list it out, and the precise order is not important, as users will not go through it in search for particular elements, I think that it does not matter that much. The same if there are just a few elements, so that deep searching is not necessary.

However, once the need for going through an ordered list appears, I would stick to the first model, as it presents the records in a way that is superior regarding comparing records one by one. Let's say you need to go through a list of names which are arranged alphabetically; it will be way more easy for you to find a name while going through each column from top to bottom, as you can focus just on the first letters of the words, which will be more complicated task when sliding with your eyes over the rest of the word, just to skip to another one. Besides, there is a need to provide more spacing between the adjacent records in the second alignment (the horizontal one) which makes it more probable that the user will slip from one line to another, thus making errors.

There is, however, an important disadvantage of the first approach - it can result in very long lists that will need scrolling and then going back to the top of the next column to continue. Thus I think the column height should be limited (in ideal situation: adaptively to the screen) so that scrolling is not necessary while going from one chunk of the list to another. It also helps with finding desired records, as the top row of the columns can be treated as keypoints, or anchors ("is the searched item after this one or before?" - once user gets to a place when it is before, he or she goes to the previous column to refine search).

So, my opinion is:

A E I
B F J
C G K
D H L

--fold--

M Q U
N R V
O S W
P T X

--fold--

Y Z

I think this is the approach learned (and so: expected) by the users from e.g. from dictionaries or atlases.

Makes logical sense, but I was looking for a more technical scientific study on this, relating to how human beings read. But I guess your right if you use basic logic.
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Sammy GuergachiMar 3 '13 at 5:19

If all items are visible at once, the first layout is better. If the columns would be long enough that they might not be visible all at once (e.g. because they're longer than a screen, or because a screen might be scrolled in such fashion as to cut off the top or bottom of the list) the second form is better.
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supercatJul 12 '14 at 18:12

While vertical lists are easier to scan, horizontal lists flow more naturally. In the western world people read left to right then top to bottom so in this sense a person may misread your vertical list as 1,5,2,6,3,7,4,8 instad of 1,2,3,4,5,7,8.